Thermoplastic polyurethane (TPU) elastomers have a broad range of flexibility and can be fabricated by a variety of methods, from injection molding to extrusion and blow molding. They also offer the performance benefits of clarity, abrasion resistance, chemical and hydrocarbon resistance, load-bearing capabilities and high tensile strengths. Accordingly, they find use in many applications which require flame resistance. Traditional flame retardants used in TPU compositions contain halogens (the so-called halogenated flame retardants). However, due to the increasing concerns about the environment and safety, there is a greater need for non-halogenated flame retardant (HFFR) materials, which poses a significant challenge to TPU-based compositions.
Liquid organic phosphates (e.g. resorcinol bis(diphenyl phosphate) (RDP), or bisphenol-A bis(diphenyl phosphate) (BDP)) are commonly used in polymers to obtain HFFR formulations. However, products made with the HFFR TPU compositions containing liquid phosphates experience migration of the phosphate flame retardants over time and, therefore, are unable to meet the non-migration requirements for some applications, such as wire and cable jacketing and insulation.